The present invention relates generally to a multigeometry image receptor holder and bite block device for use in radiographing teeth involved in dental procedures, such as endodontic, periodontic or oral surgery treatment. More particularly, the present device relates to a bite block and image receptor holder assembly which is individually rotatable about one or more axes so as to achieve a precise exposure angle for intraoral radiography, thus substantially reducing the irradiated cross-sectional area.
Endodontic treatment generally requires a battery of radiographic exposures to evaluate the pathologic state of the pulp of a damaged or diseased tooth. It is often necessary to create controlled radiographic image distortion to gain a clearer view of any overlapping roots, canals, etc., which may exist in and around the tooth. A practitioner can more accurately gauge the depth and position at which any such structure or object appears in or around the tooth by taking multiple radiographic images of the tooth from varying positions and applying the buccal object rule. The buccal object rule predicts the distortion caused by changing the angle with which the beam strikes the film.
Use of controlled image distortion requires that views be reproducible so that a particular image can be compared to a similar image taken at a later time. The radiographic view must remain constant with each exposure to insure that the variations observed in later radiographs are not caused by changing the angle of exposure. If the same view, or angle of exposure, is not maintained in each radiograph, then the changes observed may be caused by the positioning of the beam, film, or object.
The object to be observed may be a suspected tumor, carious lesion, or other hard structures of either animals or humans. In periodontics, it may be an infrabony pocket. In endodontics the observed object may be a periapical pathologic radiolucency.
In endodontic treatment, an instrument (usually a file) is placed within the pulp of the tooth. Since the file normally protrudes beyond the occlusal surface of the tooth, it is impossible to have the patient bite down on the bite block of a conventional image receptor holder to radiograph the tooth and file. Thus, any bite block and image receptor holder setup which is used in endodontic treatment must accommodate this problem by providing an offset between the bite block and the image receptor holder.
Several problems exist in utilizing conventional radiographic techniques in analyzing a tooth during endodontic treatment. One problem is the repeated exposure of the patient to overly broad areas of irradiation. Study has long shown that repeated x-ray exposure greatly increases the incidence of genetic or somatic abnormalities and promotes the development of malignant disease. While there exists considerable controversy on this subject, most authority concurs in the opinion that the incidence of abnormality or carcinoma increases in direct proportion to the Roentgen exposure/rad dose. Therefore, the greater the number of exposures, the greater the risk.
The risk of excessive radiation is increased during endodontic procedure because of the need to take multiple radiographs of the diseased tooth. In conventional oral diagnosis, one to two x-ray exposures are normally sufficient to fully analyze a tooth or adjacent group of teeth for disease, alignment, structure, etc. However, in endodontic treatment, the use of controlled image distortion often necessitates the placement of the radiographic film about the outer periphery of the x-ray exposure area, thus resulting in a number of inconclusive or "bad exposures." To compensate for these "bad exposures", the x-ray exposure field is often larger than required for imaging in order to bring the film well within the irradiated area. The x-ray beam is directed through a position indicating device ("PID") attached to the x-ray machine. The PID is typically round, rather than coincident with the rectangular area of the film thus resulting in a larger area being irradiated. This increase in the size of the irradiated field thus exposes unnecessary tissue to the risk of x-ray exposure. Also, the number of exposure is often multiplied because of the need to take duplicate exposures.
Several attempts have been made to design a bite block and image receptor holder device which would alleviate many of the problems encountered in endodontic treatment. One such design is seen in U.S. Pat. No. 4,598,416. This patent relates to a bite block and image receptor holder device having an adjustable support arm which may be pivoted in either a horizontal or vertical plane relative to the x-ray source. Rigidly attached to this support arm is a bite block and image receptor holder assembly. The film holding arm is offset from the bite block so that the x-ray film can be held securely behind the tooth to be x-rayed, despite the presence of files or other instruments in or about the tooth.
Disadvantages of this design include the lack of flexibility in positioning the bite block assembly relative to the x-ray source. In this design, the multiple pivot point is positioned on a support arm some distance from the bite block and image receptor holder assembly. No provision is made for an adjustment within the mouth of the patient so as to more precisely accommodate files or other instruments remaining in the mouth during the radiographic exposure, or to otherwise accommodate dental incongruities peculiar to any given individual.
Lack of flexibility in this design also requires an unnecessarily large area of irradiation. In operation, the alignment ring of this device is slidably attached to the long cone of the x-ray machine. The support arm members are then adjusted relative to each other to achieve a desired degree of angulation in both a horizontal and vertical plane. However, since the film holder and bite block assembly rotates a relatively long distance from the film, the cross section of the x-ray field (beam) must be kept fairly large in order to irradiate the film positioned behind the subject tooth. Therefore a round PID, as discussed above, must be used. Such a broad irradiation profile, especially when conducted over a period of time, often results in unnecessary x-ray exposure.